Medical imaging devices such as e.g. magnetic resonance imaging devices are required to be connected to different voltage supply networks throughout the world, e.g. to voltage supply networks having nominal voltages between 380 V and 480 V. However, an actual voltage of these voltage supply networks can deviate in this case by up to 10% from the nominal voltage during everyday operation. A further problem exists here in that when current is drawn off in these voltage supply networks a further voltage drop occurs due to an only finitely small internal mains supply resistance. Said further voltage drop is estimated to be 5% of the nominal voltage, for example.
In order to solve this problem, power supply equipment for magnetic resonance imaging devices is already known in the prior art in which a transfer ratio of a power supply transformer is changed by switching in or switching out turns at a primary winding unit in such a way that a supply voltage which is present at a secondary winding unit remains as constant as possible. For this purpose, the mains supply transformer has taps that are arranged at an equal distance from one another. In this case the switching in and/or switching out of individual turns of the primary winding unit can be effected by changing the tap connections or by using regulated electronic mains supply components and/or by electronic switching units that can be actuated electromotively and/or automatically. For example, a controller can effect a selection for a switching unit here by measuring a mains supply voltage that is currently present and/or by comparing the voltage that is present on the secondary side of the transformer with a reference value. However, the quality of the voltage stabilization here depends on the number of switching units that can be switched.
It is also known to tolerate dynamic deviations from a set nominal voltage, such as e.g. fluctuations in the supply network, in most cases by configuring redundancy in a gradient coil unit and/or in a radio-frequency antenna unit. Thus, for example, the gradient coil unit and/or the radio-frequency antenna unit can be designed for a maximum permitted voltage which still allows operation of the gradient coil unit and/or the radio-frequency antenna unit at a maximum overvoltage, while sufficient power reserves are still present in respect of a slew rate or a pulse power in the case of a minimum undervoltage. However, the overdimensioning of the gradient coil unit and/or the radio-frequency antenna unit involves significant additional costs here in comparison with an optimal design of the gradient coil unit and/or the radio-frequency antenna unit.